Buggy code:
public class PatientProfileController { @ FXML private TableView < MedicalStaff > assignedStaffTable ; @ FXML private TableColumn < MedicalStaff , String > positionColumn ; @ FXML private TableColumn < MedicalStaff , String > firstNameColumn ; @ FXML private TableColumn < MedicalStaff , String > lastNameColumn ; @ FXML private TableView < Caregiver > careGiversTable ; @ FXML private TableColumn < Caregiver , String > caregiverNameColumn ; @ FXML private TableColumn < Caregiver , String > birthdayColumn ; @ FXML private TableColumn < Caregiver , String > relationColumn ; @ FXML private TableColumn < Caregiver , Boolean > inFamilyColumn ; @ FXML private TableView < Contact > contactInfoTable ; @ FXML private TableColumn < Contact , String > addressColumn ; @ FXML private TableColumn < Contact , String > phoneColumn ; @ FXML private TableColumn < Contact , String > emailColumn ; @ FXML private TableView < Meal > menuTable ; @ FXML private TableColumn < Meal , String > foodColumn ; @ FXML private TableColumn < Meal , Number > caloriesColumn ; @ FXML private TableColumn < Meal , Number > ratingColumn ; @ FXML private TableColumn < Meal , String > notesColumn ; @ FXML private TableView < Pet > petTable ; @ FXML private TableColumn < Pet , String > petNameColumn ; @ FXML private TableColumn < Pet , String > speciesColumn ; @ FXML private TableColumn < Pet , Boolean > allergyFriendlyColumn ; @ FXML private Label nameLabel = new Label ( ) ; @ FXML private Label idLabel = new Label ( ) ; @ FXML private Label phoneLabel = new Label ( ) ; @ FXML private Label emailLabel = new Label ( ) ; private MainApp mainApp ; @ FXML private void initialize ( Patient patient ) { caregiverNameColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . nameProperty ( ) ) ; birthdayColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . birthdayProperty ( ) ) ; relationColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . relationProperty ( ) ) ; inFamilyColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . inFamilyProperty ( ) ) ; ObservableList < Caregiver > caregivers = MainApp . getDatabaseHandler ( ) . searchPatientCaregiver ( patient ) ; careGiversTable . setItems ( caregivers ) ; firstNameColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . getFirstNameProperty ( ) ) ; lastNameColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . getLastNameProperty ( ) ) ; positionColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . positionProperty ( ) ) ; ObservableList < MedicalStaff > personData = MainApp . getDatabaseHandler ( ) . searchPatientAssignedStaff ( patient ) ; assignedStaffTable . setItems ( personData ) ; foodColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . foodProperty ( ) ) ; caloriesColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . caloriesProperty ( ) ) ; <START_BUG> ratingColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . getRating ( ) ) ; <END_BUG> notesColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . notesProperty ( ) ) ; ObservableList < Meal > meals = MainApp . getDatabaseHandler ( ) . searchPatientMeal ( patient ) ; menuTable . setItems ( meals ) ; petNameColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . nameProperty ( ) ) ; speciesColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . speciesProperty ( ) ) ; allergyFriendlyColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . allergyFriendlyProperty ( ) ) ; ObservableList < Pet > pets = MainApp . getDatabaseHandler ( ) . searchPatientPet ( patient ) ; petTable . setItems ( pets ) ; addressColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . addressProperty ( ) ) ; phoneColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . phoneProperty ( ) ) ; emailColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . emailProperty ( ) ) ; careGiversTable . getSelectionModel ( ) . selectedItemProperty ( ) . addListener ( ( observable , oldValue , newValue ) -> showCareGiversContactInfo ( newValue ) ) ; } public void setMain ( MainApp mainApp ) { } public PatientProfileController ( IDisplayable user ) { } private void showCareGiversContactInfo ( Caregiver caregiver ) { } }

Fix:
ratingColumn . setCellValueFactory ( ( cellData ) -> cellData . getValue ( ) . ratingProperty ( ) ) ;